1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of reducing a time delay in lighting.
2. Discussion of the Related Art
With the rapid development in various fields of electronic devices, such as mobile phones, PDAs (Personal Digital Assistants), computers and large-screen TVs, the need for a flat panel display device applicable to such devices has recently been increased.
Flat panel display devices, such as an LCD (Liquid Crystal Display), a PDP (Plasma Display Panel), an FED (Field Emission Display), a VFD (Vacuum Fluorescent Display) and the like have been actively studied. However, considering the technology for mass production, facilitation of a driving unit and implementation of high-definition, the demand for the liquid crystal display (LCD) devices continues to increase.
The liquid crystal display device is a display device using optical anisotropy of liquid crystal, and implements an image by controlling optical transmissivity of the liquid crystal using an electric field.
Such liquid crystal display device includes a liquid crystal panel for displaying an image. Here, since the liquid crystal panel is a non-emitting device, a separate device for supplying light to the liquid crystal panel, called a “backlight unit,” is needed.
The backlight unit is an optical source for emitting light, and may include a Cold Cathode Fluorescence Lamp (CCFL) and an External Electrode Fluorescent Lamp (EEFL), or other light source.
For example, the fluorescent lamp is formed as a transparent tube having a cylindrical shape. An inner wall of the lamp is coated with a fluorescent material and an electrode is formed at both ends of the tube. In general, the tube is filled with a mixed gas of several tens of torr and a predetermined amount of mercury.
In this fluorescent lamp, when a high voltage is applied to the electrode, electrons in the tube are drawn to the electrode, moving at high speed, and then collide with the electrode. As a result, secondary electrons are emitted to initiate discharge.
However, if the fluorescent lamp is kept in darkness for a long time, the electrons in the tube completely disappear. Accordingly, even though a voltage is applied to the electrode, the process of colliding electrons in the tube with the electrode to emitting the secondary electrons does not easily occur because there are few or no electrons in the tube before the voltage is applied. Thus, a time during which a current does not flow in the tube continues, causing a delay in lighting. This phenomenon occurs in proportion to the time which the lamp is left alone in the darkness.
Such time delay in lighting may cause a problem of displaying an image in the liquid crystal display device when the liquid crystal display device is left alone in the darkness for a long time. Therefore, light is not emitted from the fluorescent lamp for supplying light to the liquid crystal panel, thereby not displaying an image.